Numerous oscillator circuits have been designed for the purpose of temperature sensing. All appear to require a component which varies with respect to some physical characteristic vis-a-vis temperature. This variation, in turn, is employed to affect the oscillator frequency, more or less, depending on design. Features of interest are often linearity, power consumption, physical size, frequency stability, quantum of frequency change versus temperature change and expense.
A fairly common practice is to employ a thermistor as a frequency determining element but a more common practice is to employ a temperature sensitive quartz crystal as the frequency determining element. Where a thermister is used to alter the frequency of an oscillator, circuit linearity and stability have proved to be unsatisfactory. When a quartz crystal has been used as a frequency determining element it has been necessary to use a crystal with a large linear temperature coefficient. These crystals must be specially cut and are relatively expensive.
The prior art does not include a relatively small, linear, low power, stable and inexpensive oscillator which may be used as a "throw-away", such as for ingestible thermometers.